Removal of Pb²⁺ from Wastewater By γ‐Fe₂O₃@SHFA Based on Alkali‐Modified Fly Ash: Performance and Mechanism

Abstract

A magnetic coagulant (γ‐Fe2O3@SHFA) is prepared by fly ash and magnetic seed (γ‐Fe2O3) doping to remove Pb2+ from wastewater. The optimum modification conditions and doping procedures are determined by three‐factor and single‐factor experiments, respectively. The coagulation mechanism and properties of γ‐Fe2O3@SHFA are investigated. The results show that when the coagulant dosage is 1.0 g L−1, pH = 5.0 ± 0.2, and the coagulation reaction time is 20 min, the maximum Pb2+ removal capacity can reach 88.72 mg g−1. The point of zero charge, zeta potential, Brunner Emmet Teller, scanning electron microscope, X‐ray diffraction, and X‐ray photoelectron spectroscopy indicate that charge neutralization and bridging action play an important role in the removal process of Pb2+. Coagulation kinetic, isothermal, and thermodynamic analyses show that the removal behavior of the magnetic coagulant on Pb2+ is dominated by physical effects, and the coagulation process is spontaneous, endothermic, and irreversible. After five reuses, the Pb2+ removal capacity of γ‐Fe2O3@SHFA decreases from 73.55 to 51.11 mg g−1, which remains at a high level.